Led lamp

ABSTRACT

A lamp including a plurality of semi-conductor light emitting junctions with a common layer of fluorescent material arranged thereover. The invention provides a lamp including a plurality of light emitting junctions mounted to at least one curved conductor so as to adopt a three-dimensional array.

FIELD OF THE INVENTION

[0001] The present invention relates to an LED lamp.

BACKGROUND OF THE INVENTION

[0002] U.S. Pat. No. 5,998,925 discloses a light emitting device whichcomprises a semi-conductor light emitting layer embedded in atransparent globe. A fluorescent material covers the semi-conductorlayer to receive the emitted light for transmission at a differentwavelength, i.e. in a predetermined colour.

[0003] To increase the intensity of the light output, additionalsemi-conductor devices may be added, such as shown in U.S. Pat. No.5,289,082, which discloses an LED lamp having a plurality ofsemi-conductive chips mounted in a translucent body. Each chip emits adiscrete light pattern, however, and that may be undesirable if thelight from the lamp is desired to have an appearance of emitting from asingle, point-like light source. In U.S. Pat. No. 5,289,082, thediscrete light outputs are combined and focussed, by specific shaping ofthe body to produce an overall light output having a requiredillumination pattern.

[0004] GB 2311126 discloses a comparatively large scale light sourcewhich includes an array of separately mounted light emitting diodeswhich appear to have respective leads hardwired to a planar conductor.The diodes are encapsulated by a lens which is used to focus the lightfrom the array.

OBJECT OF THE INVENTION

[0005] The present invention seeks to provide an alternative form of LEDlamp which can provide high intensity output by utilising a plurality oflight emitting diodes, whilst maintaining the appearance of asubstantially point source of illumination.

SUMMARY OF THE INVENTION

[0006] In accordance with the present invention, there is provided alamp including a plurality of semi-conductor light emitting junctionswith a common layer of fluorescent material arranged thereover, whereinthe junctions are provided in a three-dimensional array.

[0007] In another aspect, there is provided a lamp including a pluralityof semi-conductor light emitting junctions with a common layer offluorescent material arranged thereover, wherein the junctions aremounted to a curved support structure so as to be arranged substantiallyon an imaginary spheroid surface.

[0008] The common layer of fluorescent material can serve to receivelight from adjacent junctions and transmit same in a distributedfashion, so that the resultant light appears, to the naked eye, to beemanating from a single point source of illumination. Further, the layercan be applied over the junctions in a single step, and that in turn canlead to substantial simplification in the procedure for constructing thelamp, as compared to formation of the discrete chips of U.S. Pat. No.5,289,082, which would need to be individually constructed or producedusing additional steps of masking and etching.

[0009] Preferably, the lamp includes a globe portion and the junctionsare embedded within the globe portion so that the lamp is formed as aunitary structure.

[0010] Preferably, the junctions are mounted to, and electricallycoupled with, at least one curved conductor.

[0011] In another broad aspect, the invention provides a lamp includinga plurality of light emitting junctions mounted to at least one curvedconductor so as to adopt a three-dimensional array, wherein the lampincludes a common layer of fluorescent material over at least adjacentjunctions.

[0012] In yet another aspect, there is provided a lamp including aplurality of light emitting junctions mounted to at least one curvedconductor so as to adopt a three-dimensional array, wherein the at leastone curved conductor includes a recess for receipt of a respective oneof the junctions.

[0013] Preferably, the at least one curved conductor is configured suchthat junctions are arranged substantially on an imaginary spheroidsurface.

[0014] The curved configuration of the conductors and, in particular,the junctions being arranged on a substantially spheroid imaginarysurface provides an advantage that the overall light generated by thelamp will appear to be coming from a generally singular small sphericalor point source.

[0015] Preferably, the recess has side walls which function as anoptical guide for controlling the direction of light transmission and/orthe angle of divergence.

[0016] Preferably, the lamp includes a globe portion, with the junctionsand the at least one curved conductor being embedded within the globeportion so that the lamp is formed as a unitary structure.

[0017] Preferably, the lamp includes a lens adapted to fit with theglobe portion, and configured to shape the light emitted from the globeportion into a predetermined pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention will be described in more detail with reference tothe drawings in which:

[0019]FIG. 1 is a side-view of an LED lamp;

[0020]FIG. 2 is a plan-view of the lamp of FIG. 1;

[0021]FIG. 3 is a circuit diagram for the lamp of FIGS. 1 and 2;

[0022]FIG. 4 is a diagrammatic cross-sectional view of a second LEDlamp;

[0023]FIG. 5 is a circuit diagram of the lamp of FIG. 4;

[0024]FIG. 6 is a cross-sectional view of the lamp of FIG. 4;

[0025]FIG. 7 is a plan view of the lamp of FIG. 4;

[0026]FIG. 8 is a representation of an illumination pattern of the lampof FIGS. 4 to 7

[0027]FIG. 9 is a plan view of a third lamp;

[0028]FIG. 10 is a circuit diagram for the lamp of FIG. 9;

[0029]FIG. 11 is a front view of the lamp of FIG. 9;

[0030]FIG. 12 is a side view of the lamp of FIG. 9;

[0031]FIG. 13 is a side view of a lens for fitting on the lamp of FIG.9;

[0032]FIG. 14 is a cross-sectional view taken along the line X-X shownin FIG. 9;

[0033]FIG. 15 is a cross-sectional view taken along the line Y-Y shownin FIG. 10; and,

[0034]FIG. 16 is a representation of the illumination pattern producedby the lamp of FIGS. 9 to 12.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0035] The lamp 1, as shown in FIG. 1, includes a globe portion 2 with acylindrical base 3 and a parabolic end 4, configured to enhanceillumination output in an axial direction of the lamp. The lamp alsoincludes first and second terminals, which are preferably in the form ofconductors 5, 6 which are embedded within the globe portion 2. The lead5 has a support platform 7 to which is mounted an integrated circuitwafer 8. In the example given, the wafer includes two junctions whichare arranged substantially adjacent each other so that a common layer offluorescent material, such as a phosphor layer, may be applied over bothjunctions. Intermediate conductors 9 to 12 electrically couple thejunctions to the respective terminals 5, 6 so that the LED junctions 14,15 are arranged in reverse polarity, as indicated in the circuit diagramFIG. 3. A resistive element 16 is provided between a further conductor13 (connecting the intermediate conductors 11 and 12) and the lead 5.

[0036] The conductors 5, 6, intermediate conductors 9 to 13, and wafer 8are all embedded within the globe portion 2 so that the lamp ispresented as a robust unitary structure. The reverse polarity of thejunctions allows the lamp to be connected to a power source withoutconcern for polarity, as compared to the case with a conventional LEDarrangement. The use of a single phosphor layer, common to each of thejunctions, also simplifies manufacture and provides an aestheticadvantage in that the light from either junction is perceived tooriginate from a single source.

[0037] In a preferred form of the LED lamp, the following specificationsmay apply: NOMINAL SIZE 9.5 mm diameter LIGHT COLOUR WHITE GLOBE COLOURWATER CLEAR LIGHT INTENSITY SUPERBRIGHT TYPICAL LIGHT OUTPUT > 500 mCd @20 mA GUARANTEED LIFE 30,000 HOURS FOCUS HALF ANGLE 15° typ. BASE STYLEINTERCHANGEABLE WITH WEDGE TYPE LAMPS LEAD DIMENSIONS 6 mm nom. OUTSIDEBASE WEDGE SUPPLY VOLTAGE 12 VOLTS nom. {>11.5<14 volts AC or DC}FORWARD CURRENT 20 +8/−3 mA @ 12 Volts FORWARD VOLTAGE 3.6 min(typ) 4.0max. @ 20 mA REVERSE VOLTAGE 5 Volts min. POWER DISSIPATION LEDJUNCTIONS 120 Mw RESISTOR 170 mW REVERSE CURRENT 50 × 10⁻³ mA max. @ 5 VINTERNAL RESISTOR 430 ohms nom.

[0038] It should, however, be appreciated that the size configurationand operating parameters of any of the component parts of the lamp mayvary, as required and the number of LED junctions may also be increasedto suit illumination needs.

[0039] A second lamp 20 is now described with reference to FIGS. 4 to 8.The lamp 20 is generally similar in construction to that of FIGS. 1 to3, in sofar as first and second terminals 21 and 22 are provided, in theform of conductors 23, 24 embedded in a globe portion 25, together withadditional conductors 26, 27. Each of the conductors 23, 26 and 27 havea respective recess 28, to profile support structure for receiving anassociated junction, indicated by reference numerals 29, 30, 31. Thejunctions are covered by a common layer of phosphor 35 and areelectrically coupled between each respective conductors 23, 26, 27 towhich they are mounted, and the adjacent conductor via intermediateconductors 32, 33, 34. In the example shown, the junctions are seriallyconnected, as represented by the circuit diagram of FIG. 5.

[0040] All of the conductors 23, 24, 26, 27 are preferably formed in atwo dimensional lead frame structure 40 shown in FIG. 6, to allow easeof manufacture and reliability in directly positioning the junctions 29,30, 31 within the globe portion 25, after application of the phosphorlayer 35. As can be seen from both FIGS. 6 and 7, the junctions 29, 30,31 are arranged in a generally linear array, with the conductors 23, 27projecting above the conductor 26 so that the overall illuminationgenerated by the junctions will be somewhat enhanced on-axis, asrepresented in FIG. 8 by curve A.

[0041] The lamp 20 may also be provided with a lens 41 which is fittedto the globe portion 25 and shaped so as to modify the light generatedby the lamp to produce, for example, the illumination patternrepresented by curve B in FIG. 8, whereby the output illumination issomewhat more evenly distributed.

[0042] Turning now to FIGS. 9 to 16, a third lamp 50 is illustrated.Again, the lamp 50 is in general similar to the previous lampconstruction in sofar as a plurality of conductors 51, 52, 53 and 54 areembedded within a unitary globe portion 55 and have light emittingjunctions 56 mounted in respective recesses 57 and covered by a commonlayer of fluorescent material 59. Each junction is again electricallycoupled to the respective conductor to which it is mounted and anadjacent conductor via intermediate conductors 58 so as to form thecircuit illustrated in FIG. 10. Each of the conductors 51 to 54, in thisinstance, however, carrying three junctions 56.

[0043] The conductors 51 to 54 are curved within the globe portion 55 soas to support the junctions on an imaginary curved surface such as aspheroid and, in that manner, the illumination generated by the lamp 50will have an appearance of emanating from a small, generally spheroidpoint like source. A lens 60 may also be provided for modifying theoutput of the junctions to produce a more even distribution pattern suchas represented by curve C in FIG. 16, which is the illumination outputobserved from a plan view of the lamp 50, i.e. when the lamp is seenfrom the same direction as viewed in FIG. 9.

[0044] In addition to modifying the light output by using the lens 60,it is also possible to arrange the conductors in any desiredconfiguration and the construction of the recesses 57 may also be usedto assist in controlling the directional output of the light emittedfrom the various junctions. In particular, the configuration of eachrecess may be such that for example, the recess side walls act asoptical guides to control the direction and/or angle of divergence oflight emitted from each junction.

[0045] More specifically, the shape of each recess and its effect on thelight output from the junctions will now be described in more detailwith reference to FIGS. 14 and 15, which show cross-sectional views ofthe relevant conductors taken along the lines X-X and Y-Y shown in FIGS.11 and 12 respectively.

[0046] The recesses 57 containing the LED junctions are positioned andshaped in the conductors 51, 52, 53 so that the beams of light emergingfrom the recesses may be combined in free space outside the lamp 50 inpredictable patterns determined by the radius of the imaginary partspherical surface designated ‘R’, the distance from the LED junction inthe recess to the intersection of the imaginary extension of the sidesof a recess—designated ‘r’ and the angle ‘A’ between the centre line 61of the lamp 50 and a centre line 62 passing through the perpendicular toany other LED junction.

[0047] The radius ‘R’ of the imaginary spherical surface is the distancefrom the intersection of those centre lines to the LED junction withinthe recess. The angle between the sides of a recess determines the valueof the ‘r’.

[0048] In the limiting case where ‘r’ is equal to or greater than ‘R”,the light from each LED junction will be shaped by the recesses intobeams which do not cross, regardless of the value of angle ‘A’. For allvalues of ‘r’ less than ‘R’ it will be possible to have the light beamfrom each LED junction coincide with the edges of the light beams fromadjacent LED junctions. The exact positioning if this instance will bedetermined by the ratio R/r and the value of angle ‘A’.

[0049] As may be appreciated from the above, the present inventionallows considerable scope for obtaining a light source using junctiondiodes, with a predetermined one of a variety of output illuminationpatterns whilst maintaining a generally simple construction. Aparticular advantage is that the various junctions are of small size andmay be configured to produce a light output which may be perceived bythe naked eye to be emanating from a single point source of light.

[0050] The above LED lamps have been described by way of non-limitingexample only, and many modifications and variations may be made theretowithout departing from the spirit and scope of the invention ashereinbefore described.

1. A lamp including a plurality of semi-conductor light emittingjunctions with a common layer of fluorescent material arrangedthereover, wherein the junctions are provided in a three-dimensionalarray.
 2. A lamp including a plurality of semi-conductor light emittingjunctions with a common layer of fluorescent material arrangedthereover, wherein the junctions are mounted to a curved supportstructure so as to be arranged substantially on an imaginary spheroidsurface.
 3. A lamp as claimed in claim 1 or 2, wherein the lamp includesa globe portion and the junctions are embedded within the globe portionso that the lamp is formed as a unitary structure.
 4. A lamp as claimedin any one of claims 1 to 3, wherein the junctions are mounted to, andelectrically coupled with, at least one curved conductor.
 5. A lampincluding a plurality of light emitting junctions mounted to at leastone curved conductor so as to adopt a three-dimensional array, whereinthe lamp includes a common layer of fluorescent material over at leastadjacent junctions.
 6. A lamp including a plurality of light emittingjunctions mounted to at least one curved conductor so as to adopt athree-dimensional array, wherein the at least one curved conductorincludes a recess for receipt of a respective one of the junctions.
 7. Alamp as claimed in claim 6, wherein the at least one curved conductor isconfigured such that junctions are arranged substantially on animaginary spheroid surface.
 8. A lamp as claimed in claim 6 or 7,wherein the recess has side walls which function as an optical guide forcontrolling the direction of light transmission and/or the angle ofdivergence.
 9. A lamp as claimed in any one of claims 5 to 8, whereinthe lamp includes a globe portion, with the junctions and the at leastone curved conductor being embedded within the globe portion so that thelamp is formed as a unitary structure.
 10. A lamp as claimed in claim 9,wherein the lamp includes a lens adapted to fit with the globe portion,and configured to shape the light emitted from the globe portion into apredetermined pattern.